Cartilage repair unit

ABSTRACT

A bio-absorbable cartilage repair system is provided for regenerating damaged or destroyed articular cartilage on a joint surface of a bone by establishing a chondrogenic growth-supporting matrix between an area of damaged or destroyed articular cartilage that has been removed and an adjacent healthy area of articular cartilage and subchondral cancellous bone. The system is an assembly of a delivery unit and a porous insert. The delivery unit is formed of bio-absorbable material and configured and dimensioned to be mounted in both an area of damaged or destroyed articular cartilage that has been removed and an adjacent healthy area of articular cartilage and cancellous bone. The delivery unit has a central body and a plurality of radially extending, flexible support arms projecting outwardly from the central body and configured and dimensioned to support the insert at least partially thereover. The insert is supported by the delivery unit, formed of bio-absorbable material, and establishes communication between the removed area and the adjacent healthy area for a chondrogenic growth-supporting matrix.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/325,957, filed Jun. 4, 1999 now U.S. Pat. No. 6,251,143.

BACKGROUND OF THE INVENTION

This invention relates to a bio-absorbable cartilage repair system forregenerating articular cartilage and, more particularly, a system whichallows for vascular invasion and cellular migration between the systemand the adjacent healthy area of articular cartilage and cancellousbone, thereby resulting in regeneration of the damaged articularcartilage.

Articular cartilage on the surface of bones in joints, most particularlythe knee, ankle and hip joints, is susceptible to deterioration causedby injury or disease. This deterioration of cartilage leads to pain andeventually loss of joint movement and more severe pain. As a result,various methods have been developed to treat and repair damaged ordestroyed articular cartilage.

Prosthetic devices are often used to replace damaged or destroyedarticular cartilage. For example, U.S. Pat. No. 4,627,853 disclosesprosthesis which are used for articular cartilage replacement. Theprosthesis are prepared by demineralization of a bone segment, thedemineralized bone segment serving as a replacement for articularcartilage.

U.S. Pat. No. 5,176,710 discloses a prosthesis for replacing bonematerial on the articulating surface of a joint. The prosthesis has aspecific modulus of elasticity so as to confer stiffness to theprosthesis, and contains concave shapes which are suitable for biologicingrowth.

U.S. Pat. No. 3,745,590 discloses a prosthesis for the repair orreplacement of joints, which prosthesis comprises a body portion,including a stem and ligamentous elements, and allows for tissueingrowth.

U.S. Pat. No. 5,123,927 discloses a knee prosthesis comprising bonecement containing an antibiotic.

U.S. Pat. No. 4,904,259 discloses a resorbable gel, including ex vivochondrocyte cells, press fit into a cartilage defect.

U.S. Pat. No. 5,270,300 discloses a scaffold into which cells grow, butwithout any blood supply from the subchondral bone.

U.S. Pat. No. 5,306,311 discloses a resorbable prosthesis suitable forbiologic ingrowth.

PCT Publication No. PCT/WO95/30383 discloses ex vivo proliferated,denuded chondrogenic cells for synthetic cartilage use in surgicallyrepairing cartilage defects.

Although there are several prosthetic devices which can be used in thereplacement of damaged or destroyed articular cartilage, prostheticdevices have several disadvantages. For example, cements which are usedto attach prosthetic devices to bones may loosen and eventually fail. Inaddition, fragmented cement can move into the joints and associatedlymph tissue and cause inflammation and further damage. Further, cementsresult in the formation of fibrous tissue between the bone and theprosthesis. Another major disadvantage associated with the use ofprosthesis is that the prosthetic device may be larger than the damagedcartilage that needs to be replaced, thereby requiring removal ofportions of healthy bone and/or cartilage in order to accommodate theprosthetic device. Hence, the need remains for a system for repairingand regenerating articular cartilage which avoids the problemsassociated with prosthetic devices.

Another means used to treat damaged articular cartilage is the placementof repair pieces onto the bone, which repair pieces substitute forcut-out pieces of cartilage. For example, U.S. Pat. No. 5,067,964discloses an articular cartilage repair piece which comprises a layer ofnon-woven, felted fibrous material which is limp and readily conformableto flat and curved surfaces. The articular cartilage repair piece isattached to the bone, for example, by bio-absorbable screws or pins orlike temporary fixation techniques. Fibrous tissue ingrowth eventuallysurrounds the repair piece thereby causing the repair piece to bepermanently attached to the bone. Although U.S. Pat. No. 5,067,964discloses an alternative method for repairing damaged articularcartilage, it does not disclose any means or method of regeneratingdamaged or destroyed articular cartilage. Hence, the need remains for asystem for regenerating damaged or destroyed articular cartilage,wherein the regenerated articular cartilage is functionally similar tonon-damaged articular cartilage.

Commonly owned U.S. Pat. Nos. U.S. Patent No. 5,632,745; U.S. Pat. No.5,749,874; and U.S. Pat. No. 5,769,899 disclose such a regeneratingsystem and are incorporated herein by reference. However, theregenerating systems disclosed therein have not proved to be entirelysatisfactory from the points of view of both the manufacturer and thesurgeon installing the same in a patient.

Accordingly, an object of this invention is to provide a system forregenerating articular cartilage.

Another object is to provide a system for regenerating articularcartilage wherein the regenerated articular cartilage is functionallysuperior to fibrous or fibrocartilagenous repairs and is functionallysimilar to non-damaged articular cartilage.

A further object is to provide a cartilage repair system for use inregenerating damaged or destroyed articular cartilage.

It is another object of the present invention to provide an embodimentof the cartilage repair system which does not employ cement ornon-bio-absorbable prosthetic devices.

It is a further object to provide an embodiment of the cartilage repairsystem for repairing bone as well where there are injuries to bothcartilage and bone.

SUMMARY OF THE INVENTION

It has now been found that the above and related objects of the presentinvention are obtained by a bio-absorbable cartilage repair system forregenerating damaged or destroyed articular cartilage on the jointsurface of a bone, which system establishes a chondrogenicgrowth-supporting matrix between an area of damaged or destroyedarticular cartilage that has been removed and an adjacent healthy areaof articular cartilage and cancellous or trabecular bone. The systemcomprises an assembly of a bio-absorbable delivery unit and a porousbio-absorbable insert. The delivery unit is formed of bio-absorbablematerial and configured and dimensioned to be mounted in both an area ofdamaged or destroyed articular cartilage that has been removed and anadjacent healthy area of articular cartilage and cancellous bone. Thedelivery unit has a central body and a plurality of radially extending,flexible support arms projecting outwardly from the central body andconfigured and dimensioned to support the insert at least partiallythereover. The insert is supported by the delivery unit, formed ofbio-absorbable material, and establishes communication between theremoved area and the adjacent healthy area for a chondrogenicgrowth-supporting matrix.

In a preferred embodiment, the insert is disposed on the upper, lower,and outer surfaces of the support arms, and the support arms have freeends circumferentially spaced from one another to define areas forreceipt of a chondrogenic growth-supporting matrix. The support armspreferably have circumferentially spaced free ends adapted to engage andat least partially spatially stabilize the insert. The support arm freeends may be horizontally or vertically barbed. The central body adjacenta bottom end thereof defines a plurality of outwardly extending flanges.

In a preferred embodiment, the insert has a top, a bottom and a sidewallconnecting the top and bottom. The bottom allows vascular invasiontherethrough, and the top and sidewall allow cellular migrationtherethrough by an adjacent healthy area of articular cartilage andsubchondral cancellous bone. The insert may include cells to facilitateestablishing such communication. The sidewall is preferably polygonal inplan. Each of the delivery unit and the insert preferably essentiallyconsists of completely bio-absorbable material which is ceramic-free anddimensionally stable in synovial joint fluid against expansion due tothe absorption thereof.

The system may additionally include retainer means for securing theinsert to the delivery unit. The retainer means is secured to a portionof the central body below the insert and bears upwardly against theinsert. The retainer means essentially consists of completelybio-absorbable material which is ceramic-free and dimensionally stablein synovial joint fluid against expansion due to the absorption thereof.

Preferably the system additionally includes a porous film formed ofbio-absorbable material securing the insert to the delivery unit. Theporous film has a central film portion disposed over the insert and aplurality of film fingers projecting outwardly from the central filmportion, downwardly and inwardly, under the support arms. Optionally,upwardly barbed retainer means are secured to the central body and bearupwardly against the film fingers. The porous film essentially consistsof completely bio-absorbable material which is ceramic-free anddimensionally stable in synovial joint fluid against expansion due tothe absorption thereof.

In another preferred embodiment, the insert is a flexible porous filmformed of bio-absorbable material secured to the delivery unit. Theporous film has a central film portion disposed over the support armsand a plurality of film fingers projecting outwardly from the centralfilm portion, downwardly and inwardly, under the support arms. Aretainer means is preferably secured to the central body and bearsupwardly against the film fingers. The porous film essentially consistsof completely bio-absorbable material which is ceramic-free anddimensionally stable in synovial joint fluid against expansion due tothe absorption thereof.

In the latter embodiment, preferably the central body defines anaperture extending longitudinally therethrough, and the insert definesan aperture extending longitudinally therethrough. A retainer means maybe secured to the central body and bears upwardly against the insert,the retainer body defining an aperture extending longitudinallytherethrough coaxial with the central body aperture. A porous filmconsisting substantially of completely bio-absorbable material maysecure the insert to the delivery unit, the porous film defining anaperture extending longitudinally therethrough coaxial with the centralbody aperture. When the insert is a flexible porous film consistingsubstantially of completely bio-absorbable material secured to thedelivery unit, the porous film may define an aperture extendinglongitudinally therethrough coaxial with the central body aperture.

In yet another embodiment, at least a portion of the delivery unitcentral body disposed below the insert defines flexible legs, the systemadditionally including means for moving the legs from a horizontallyretracted orientation enabling removal of the assembly to a horizontallyexpanded orientation fixing the assembly in place. Preferably, theflexible legs are resilient, and the moving means is retractable toenable movement of the legs from the expanded orientation to theretracted orientation.

Preferably, the insert consists substantially of a bio-absorbablematerial selected from the group consisting of hyaluronic acid,polyglycolic acid, collagen, polylactic acid, fibrin clot, periostealcells, polydioxane, polyester, alginate and combinations thereof, whilethe delivery unit comprises a bio-absorbable material selected from thegroup consisting of hyaluronic acid polyglycolic acid, polylactic acid,alginate and combinations thereof.

In a preferred embodiment, the insert includes a repair factorreleasably disposed in the insert to assist in establishing thechondrogenic growth-supporting matrix. The repair factor may be a growthfactor, preferably one selected from the group consisting of fibroblastgrowth factor, transforming growth factor beta, insulin, insulin likegrowth factor, platelet derived growth factor and combinations thereof.Alternatively, the repair factor may be an attachment factor, preferablyone selected from the group consisting of fibronectin, RGD polypeptideand combinations thereof, or a cell factor, preferably one selected fromthe group consisting of stem cells, periosteal cells, and cellscontaining genes specific for cartilage formation and combinationsthereof. Indeed, the repair factor preferably includes growth,attachment and cell factors.

The delivery units of the assemblies are disposed within the bone andthe removed area, and the inserts of the assemblies establish thechondrogenic growth-supporting matrix over a substantial portion of theremoved area. The insert of the assemblies may be polygonal inconfiguration and interfitting.

The cartilage repair system preferably includes means precludingrelative rotation of the delivery unit and the insert in the deliveryunit.

The present invention further encompasses a cartilage repair systemadapted to be mounted on the joint surface of a bone to establish achondrogenic growth-supporting matrix, wherein the system comprises abio-absorbable delivery unit configured and dimensioned to be mounted onthe bone, the unit including a support frame and means for mounting theunit in the bone, and a porous bio-absorbable insert supported by thesupport frame to provide a chondrogenic growth-supporting matrix.Preferably the support frame is constructed to allow vascular invasionand cellular migration to the insert.

In one preferred embodiment of the present invention, the delivery unitis a subassembly of two separately formed components, one of thecomponents being configured and dimensioned to be mounted in both anarea of damaged or destroyed articular cartilage that has been removedand an adjacent healthy area of articular cartilage and cancellous bone,and the other component having a central body and a plurality ofradially extending, flexible support arms projecting outwardly from thecentral body and configured and dimensioned to support the insert atleast partially thereover. Preferably, the one of the components definesa longitudinal aperture therethrough and the central body of the othercomponent is configured and dimensioned to at least partially passthrough the aperture. The subassembly may be assembled with the insertprior to use. At least one of the components includes means forretaining the components together after assembly, and the subassemblyincludes retainer means for bearing on a portion of the insertintermediate the two components to lock the delivery unit portion inplace.

Additionally, the present invention encompasses a bio-absorbablecartilage repair system comprising an assembly consisting essentially oftwo delivery units and a single flexible porous insert. The insert issupported by both of the delivery units, is formed of flexiblebio-absorbable material, and establishes communication between theremoved area and the adjacent healthy area for a chondrogenicgrowth-supporting matrix. The delivery units are configured anddimensioned to enable them to be disposed along a common longitudinalaxis, facing each other, and connected only by the insert for insertioninto a patient. The assembly is then unfolded to enable the deliveryunits to be separately mounted along generally parallel longitudinalaxes, side-by-side. Preferably the insert defines a pair of insertportions, each insert portion extending over the top of a respective oneof the delivery units, and a connecting portion of reduced widthfoldably connecting the insert portions together.

Further, the present invention encompasses a bio-absorbable cartilagerepair system comprising an assembly of a delivery unit and a porousinsert. The delivery unit has a central body and an inwardlycompressible plurality of spirally or helically extending, flexiblesupport arms projecting outwardly from the central body and configuredand dimensioned to support the insert at least partially thereover.Preferably, the system comprises at least two of the assemblies, eachdelivery unit being mounted side-by-side such that at least one supportarm of one of the delivery units inwardly compresses at least onesupport arm of the other of the delivery units. The at least one supportarm of one unit would overlap at least one support arm of the other unitif at least one support arm were not inwardly compressed.

In a preferred embodiment of the present invention, a top layer of theinsert contains a chondrogenic growth-supporting matrix, and a lowerportion of the insert contains an osteogenic growth-supporting matrix,the assembly being configured and dimensioned to be disposed with thechondrogenic growth-supporting matrix adjacent a healthy area ofarticular cartilage and the osteogenic growth-supporting matrix adjacenta healthy area of subchondral cancellous bone, thereby to establishchondrogenic and osteogenic growth-supporting matrices in removed areasof damaged or destroyed articular cartilage and subchondral bone,respectively.

In another preferred embodiment, the delivery unit includes a headportion and a stem portion, the head and stem portions being pivotallyjoined together, one of the portions preferably defining a ball and theother of the portions preferably defining a socket. Optimally the stemportion defines a ball at a distal end, and the head portion defines asocket at a proximal end, the ball being pivotally maintained in thesocket such that the head portion is pivotable relative to the stemportion.

BRIEF DESCRIPTION OF THE DRAWING

The above brief description, as well as further objects, features andadvantages of the present invention, will be more fully understood byreference to the following detailed description of the presentlypreferred, albeit illustrative, embodiments of the present inventionwhen taken in conjunction with the accompanying drawings wherein:

FIG. 1 is an exploded isometric view of a first embodiment of theassembly of the cartilage repair system;

FIG. 2 is an isometric assembly view thereof;

FIG. 3 is an isometric view of the delivery unit alone;

FIG. 4 is a sectional view thereof taken along the line 4—4 of FIG. 3;

FIG. 5 is a sectional view thereof taken along the line 5—5 of FIG. 3;

FIG. 6 is a partially exploded isometric view of a second embodiment ofthe present invention;

FIG. 7 is a fragmentary exploded isometric view of a third embodiment;

FIG. 8 is a partially exploded isometric view of the third embodiment;

FIG. 9 is a partially exploded sectional view of a fourth embodiment;

FIG. 10 is an isometric assembly view of the fourth embodiment;

FIG. 11 is an exploded isometric view of a fifth embodiment;

FIG. 12A is a partially exploded isometric view of the fifth embodimentundergoing sonic welding;

FIG. 12B is a fragmentary sectional view of the fifth embodiment;

FIG. 13A is an exploded side elevational view, partially incross-section of a sixth embodiment;

FIG. 13B is a side elevational assembly view of the sixth embodiment;

FIG. 14 is a side elevational view, partially in cross-section, of aseventh embodiment;

FIG. 15 is an isometric view of the seventh embodiment;

FIG. 16 is a side elevational view, partially in cross-section, of aneighth embodiment;

FIG. 17 is an exploded isometric view of the eighth embodiment;

FIG. 18 is a side elevational view, partially in cross-section, of aninth embodiment, with the insert being inserted into the delivery unit;

FIG. 19 is a view similar to FIG. 18, but shows the insert fullyinserted into the delivery unit;

FIG. 20 is an isometric assembly view of the ninth embodiment;

FIG. 21 is a bottom plan view of an insert of the tenth embodiment;

FIG. 22 is a top plan view of the tenth embodiment, with upper layersbeing removed to reveal details of internal construction and with thedelivery unit shown in its original position in dotted line and in itsfinal position in solid line;

FIG. 23 is an isometric assembly view of the tenth embodiment;

FIG. 24 is a top plan view of the eleventh embodiment;

FIG. 25 is a side elevational view, partially in cross section, of theeleventh embodiment;

FIG. 26 is an exploded side elevational view of the eleventh embodimentwith the insert being removed for pedagogic purposes;

FIG. 27 is a bottom plan view of the lower portion of the assembly ofFIG. 26;

FIG. 28 is a side elevation assembly view of the eleventh embodiment,partially in cross section;

FIGS. 29 and 30 are top plan and side elevational views, respectively,of the twelfth or duplex embodiment in an unfolded orientation;

FIGS. 31 and 32 are top plan and side elevational views, respectively,of the twelfth embodiment in a folded orientation;

FIG. 33 is a top plan view of two contiguous twelfth embodiments and anon-duplex embodiment;

FIG. 34 is a top plan view of a single twelfth embodiment contiguous totwo non-duplex embodiments, one on either side;

FIG. 35 is a top plan view of a thirteenth or compressible armembodiment, with portions of the insert cut away to reveal details ofinternal construction;

FIG. 36 is a top plan view of three assemblies of the thirteenthembodiment in contiguous relationship with portions of the insertpartially cut away;

FIGS. 37-40 are schematic top plan views illustrating the method ofinstalling contiguous assemblies of a variant of the thirteenthembodiment into a work area, with the compression tubing used in themethod illustrated in phantom line and with portions of the insertpartially cut away;

FIGS. 41-42 are schematic top plan views illustrating an alternativemethod of installing contiguous embodiments;

FIG. 43 is a top plan view of a variant of the thirteenth embodiment,with portions of the insert partially cut away;

FIG. 44 is a side elevational view, partially in section, of a variantthe thirteenth embodiment; and

FIG. 45 is a side elevational view, partially in section, of thefourteenth embodiment.

It will be appreciated that in various views (e.g., FIGS. 15, 20, 23, 24and 35-44) the insert has been partially cut away in order to revealdetails of internal construction.

Elements of the several embodiments which have the same or likestructure and/or perform the same or like functions are identified bythe same reference numerals. For composite reference identifications,the upper case following the reference numeral indicates the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawing, and in particular to FIGS. 1-5 thereof,therein illustrated is a preferred first embodiment of a cartilagerepair system according to the present invention, generally designatedby the reference numeral 10. More particularly, the preferred cartilagerepair system 10 is comprised of an assembly generally designated 12(one being illustrated, but it being understood that the requisitenumber is determined by the extent of the damaged area). Each assembly12 is in turn comprised of a bio-absorbable delivery unit 14 (seen alonein FIGS. 3-5) and a porous bio-absorbable insert 16 (seen with thedelivery unit 14 in FIGS. 1 and 2). The delivery unit 14 is configuredand dimensioned to be mounted in both the area from which damaged ordestroyed articular cartilage has been removed and the adjacent healthycancellous bone area of the bone. The porous insert 16 is supported bythe delivery unit 14 and establishes communication between the removedarea (that is, the area from which the damaged or destroyed articularcartilage has been removed) and the adjacent healthy area for achondrogenic growth-supporting matrix, thereby promoting vascularinvasion and cellular migration to achieve articular cartilageregeneration.

While the system 10 is discussed herein as being used to regeneratedamaged or destroyed articular cartilage on the femoral knee jointsurface K, those skilled in the medical arts will readily appreciatethat the system 10 is equally useful in other articular joints such asthe shoulder, hip, and the like. The extent of the damaged or destroyedarticular cartilage on the surface of the bone will determine whetherthe system 10 employs a single assembly 12 or a plurality of assemblies12. The illustrated assembly 12 (and in particular the delivery unit 14thereof) is polygonal in plan and interfitting—that is, disposed suchthat two assemblies 12 can be mounted in contiguous abutting contact ina side-by-side relationship. The polygonal nature of the periphery ofthe assemblies permits interfitting of the assemblies 12 and is thuspreferred where a plurality of the assemblies 12 are to be used tocompletely cover or tile a designated area of the bone. However, whereonly a single assembly 12 will be used, other configurations, such as acircular configuration, may be preferred.

While theoretically it might be possible to create in a singlemanufacturing operation (e.g., one employing photolithography) aunitary, one-piece, integral assembly 12 which performs the functions ofboth the delivery unit 14 and the insert 16, the present inventionpreferably utilizes at least two separate and independently formedcomponents—namely, the delivery unit 14 and the insert 16. As will bediscussed below in detail, the insert 16 can be made of a relativelywide variety of different materials and may even include a repair factor(such as a growth factor or an attachment factor) releasably disposedtherein to assist in establishing the chondrogenic growth-supportingmatrix.

Accordingly, the two-component nature of the assembly 12 of the presentinvention enables the insert 16 to be selected from a supply ofdifferent inserts 16 at the time of surgery so as to meet the particularneeds of the patient at the time with regard to the basic composition ofthe insert 16 and any repair factor composition therein. Again, becauseof the differing natures of the insert 16 (and any repair factorstherein) and its delivery unit 14, it may be necessary for particulartypes of inserts 16 to be stored before use in different environmentsfrom the delivery units 14—for example, in order to provide appropriatepreservation of the repair factor. Finally, the delivery unit 14 andinsert 16 of an assembly 12 must have different functionalcharacteristics which would be difficult to achieve through knownmanufacturing techniques in an integral, one-piece, unitary element.Thus, as will be discussed below, the delivery unit 14 must havesufficient strength and integrity to enable it to be tamped into thebone without significant bending or deforming, while the insert 16 ispreferably a flexible porous material in the form of a matrix to enableit to fit onto the delivery unit 14 and thereby provide a chondrogenicgrowth-supporting matrix positioned by the delivery unit 14.

The system 10 includes, in addition to the assembly 12, a retainer meansgenerally designated 20 and a porous film generally designated 22.

The delivery unit 14 is formed of bio-absorbable material as configuredand dimensioned to be mounted in both an area of damaged or destroyedarticular cartilage that has been removed and an adjacent healthy areaof articular cartilage and cancellous bone. The delivery unit 14 has anelongate central body 26 and a plurality of radially extending flexiblesupport arms 28 projecting outwardly from the central body (or at leastthe longitudinal axis passing through the central body).. The arms 28are configured and dimensioned to support the insert 16 laterallythereabout, at least partially thereover, and, optionally, therebelow.As illustrated in the first embodiment, the support arms 28 have freeends circumferentially spaced from one another to define areas forreceipt of a chondrogenic growth-supporting matrix. Further, the supportarms 28 have circumferentially spaced free ends adapted to engage and atleast partially stabilize the insert 16. The support arms 28 arehorizontally barbed to assist in retaining the insert in place on thedelivery unit 14. (Alternatively, as illustrated in other embodiments,the support arm free ends may be vertically barbed.)

For reasons which will become apparent hereinafter, the elongate body 26of the delivery unit 14 is preferably oval in shape, with the outersurface of the oval defining outwardly projecting steps 32 for engagingbone.

As illustrated, the delivery unit 14 has six support arms 28 regularlyspaced about the central axis thereof, although clearly greater orlesser numbers of arms may be used.

The insert 16 is preferably hexagonally shaped, with the number of itssides matching the number of radial arms 28 of the delivery unit 14.Clearly, a greater or lesser number of sides may be defined by theinsert 16, although preferably the number of sides is always equal tothe number of radial arms 28. The insert 16 is preferably disposed inthe first embodiment on the upper, lower and outer surfaces of thesupport arms 28. The insert 16 has a top 40, a bottom 42, and a sidewall44 connecting the top 40 and bottom 42. The bottom 42 allows vascularinvasion and cellular migration therethrough while the top 40 andsidewall 44 allow cellular migration therethrough by an adjacent healthyarea of articular cartilage and subchondral cancellous bone. Preferably,the sidewall 44 is polygonal in plan to enable a plurality of thesystems to be used in close proximity to occupy an enlarged area ofdamaged or destroyed articular cartilage that has been removed.

The first embodiment of the system 10 additionally includes a porousfilm 22 formed of bio-absorbable material for securing the insert 16 tothe delivery unit 14. More particularly, the porous film 22 has acentral film portion 50 disposed over the insert 16 and a plurality offilm fingers 52 projecting outwardly from the central film portion 50and being wrapped downwardly and inwardly under the support arms 28.Preferably, the porous film 22 has a plurality of film fingers 52 equalto the number of sides of the insert 16 and thus the number of radialarms 28.

The first embodiment of the system additionally includes a retainer 20secured to the central body 26 and bearing upwardly against the filmfingers 52, thereby to maintain the film 22 in position to maintain theinsert 16 on the delivery unit 14. The central aperture 56 of retainer20 is enlarged and elongated to enable passage of the retainer 20 overthe outwardly extending steps 32 and locking flange 70 of the centralbody 26. Subsequent rotation of the retainer 20 about 90° locks theretaining means 20 in place against the film fingers 52. Alternatively,instead of rotation, one of the bottom surface of the film fingers 52and the top surface of the retainer 20 is barbed so that it engages theother when the retainer 20 and fingers 52 approach.

In the preferred embodiment illustrated, the upper surface of theretainer 20 defines a plurality of upwardly extending barbs 21, and thebottom surface of each support arm 28 defines one or more downwardlyextending barbs 21′. Such an arrangement securely locks the film fingers52 wrapped under the support arms 28 in place between the retainer 20and support arms 28, thereby to prevent accidental dislodgment thereof.Clearly, the upwardly directed barbs 21 may be used apart from thedownwardly directed barbs 21′, and vice versa.

It will be appreciated that each of the delivery unit 14, insert 16,porous film 22 and retainer 20 essentially consists of substantiallycompletely bio-absorbable material which is dimensionally stable insynovial joint fluid against expansion due to the absorption thereof.Such material excludes ceramics and the like.

Each of the delivery unit 14, the insert 16, the retainer 20 and theporous film 22 defines one or more aligned small apertures or bores 30extending therethrough along a central longitudinal axis to enable useof the system with a guidewire. As illustrated, the small aperture orbore 30 in the retainer 20 is part of a larger central aperture 56 andcannot be separately seen.

It will be appreciated that, even though the porous film 22 isillustrated as containing an aperture or bore 30 aligned with theapertures or bores 30 of the insert 16 and the delivery unit 14, in factthe porous film 22 may be imperforate with the task of creating anaperture or bore 30 therein being left to the surgeon. When the system10 is assembled, the bore 30 passes through the porous film 22,sub-assembly of radial arms 28, central body 26 and retainer 20.

In order to enable the insert 16 to function as a chondrogenicgrowth-supporting matrix, it must have access to vascular invasion andcellular migration to regenerate the articular cartilage defect. Suchaccess is provided on the internal periphery of the insert 16 by thebore 30 and on the external periphery of the insert 16 by the porousfilm 22 on the support arms 28. The porous film 22 enables indirectcontact of the insert 16 with the adjacent healthy articular cartilageor with any adjacent repair assemblies 10. The porous film 22 allowscellular migration to the insert 16. The entire top surface 40 of theinsert 16 is exposed to the articular environment of the affected joint,and a substantial portion of the bottom surface 42 of the insert 16 isexposed to the cancellous bone. The degree of communication between thearea of removed damaged articular cartilage and the healthy cancellousor trabecular bone, is determined by the size, shape and placement ofthe system components and is selected to provide a desirable level ofcommunication without unduly deleteriously affecting the strength of thedelivery unit 14.

The delivery unit 14 is flexible and preferably resilient, so that itdoes not bend or deform unduly under expected pressures. It ispreferably integrally molded. It is critical that the delivery unit 14be made of a bio-absorbable material (e.g., without ceramics) such asthose well known in the implant art. For example, it is preferably madeof polyglycolic acid, polylactic acid or combinations thereof (e.g.,copolymers and mixtures thereof).

Several delivery units 14 can be placed contiguously in an area ofremoved damaged articular cartilage such that a large portion of theremoved area will be filled with the assemblies 12. In this case, thedelivery units 14 are preferably regular polygons and interfitting in anabutting and contiguous relation. A circular delivery unit may be usedwhere only one delivery unit is employed or where only partial coverageof the removed area is desired. Indeed, as set forth hereinbelow indetail, special circular delivery units may be particularly desirable intiling a work area.

The insert 16 is made substantially of porous material in the form of amatrix or sponge, preferably defining at least 95% voids by volume, sothat it can serve as a biological scaffold for an invasion of cells toregenerate the articular cartilage. It typically has the felt-like feelof a non-woven fabric. The insert 16 may be manually bendable orflexible so that one can push, press or snap the same onto the deliveryunit 14. It is critical that the insert 16 consists substantially(typically at least 95% of the inorganic components by weight) of abio-absorbable material selected from the group consisting of hyaluronicacid (e.g. as a fiber matrix), polyglycolic acid (e.g., as fibermatrix), collagen, including type I collagen (e.g., as a sponge matrix),polylactic acid (e.g. as a fiber matrix), fibrin clot (which can befilled and molded into the delivery unit), collagen gel (which can beoverlayed into a polyglycolic acid matrix), polydioxane, polyester,alginate or combinations thereof. The polylactic acid, and to a lesserdegree the hyaluronic acid, polyglycolic acid, and alginate, contributeto the hardness and longevity (i.e., life in situ after implantation) ofthe insert 16.

The insert may be annealed (i.e., heat-treated or cooked) to modify itscrystallinity and thus its hardness and longevity.

In addition, in a preferred embodiment of the invention, the insert 16can contain within the matrix “repair factors” such as growth factorsand/or attachment factors and/or cell factors well known in the medicalarts. For example, the insert 16 can contain, as growth factors,fibroblast growth factor (acidic or basic), transforming growthfactor-beta (1, 2, 3 or one of the members of the supergene family ofTGF-beta, such as bone morphogenic protein (BMP)), insulin, insulin-likegrowth factor 1 & 2 (IGF), platelet-derived growth factor orcombinations thereof. The attachment factors which can be used in theinsert include fibronectin, RGD polypeptide and combinations thereof.Typically, the repair factors total less than 1% by weight of theinsert, but can range up to 10% depending on the factors' specificactivities and release kinetics. The repair factors may be chemicallycombined with the basic implant composition (e.g., during polymerizationthereof) or may be added to an already formed basic implant composition.in the former case, additional repair factor will typically becomeavailable as the basic implant composition biodegrades. As the cellfactors, the insert may also include at least partiallynon-bio-absorbable cartilage or cartilage progenitor cells (such asisolated periosteal cells) which may be cultured in the insert materialor grown ex vivo and then overlaid, instilled or injected at the time ofsurgery into the insert material. Other cell types, such as mesenchymalstem cells, tissue (e.g., small intestine submucosa), chondrocytes,cells containing genes specific for cartilage formation and maintenanceof phenotype (e.g., collagen type II, aggrecon, hedgehog genes, etc.)and genetically engineered cells may also be a part of or added to theinsert material. Indeed, bio-absorbable or essentially bio-absorbablepieces of ex vivo cartilage may be employed in the insert.

After surgical removal of the damaged or destroyed articular cartilage,the elongate member 26 of delivery unit 14 (extending downwardly fromthe support arms 28) is placed into the cancellous bone through thesubchondral bone plate located below the damaged articular cartilagearea so that the support arms 28 are adjacent the subchondral boneplate. The elongate member 26 has a blunt bevelled bottom so that it canbe placed easily into the cancellous bone, which is a soft region of thebone. The bottom of the elongate member 26 is preferably blunt so thatthe bottom does not break as the elongate member 26 is being placedinside the cancellous bone. When the elongate member 26 is placed intothe soft cancellous bone, the cancellous bone is displaced by, and thenreforms around the elongate member 26. In this manner, the elongatemember 26, and thereby the entire cartilage repair system 10, is held inplace.

When the delivery unit 14 is placed in the bone, the insert 16, andtypically the top surface of the elongate member 26, is coplanar withundamaged articular cartilage. The support arms 28 and the insert 16 arenot placed inside the bone, but rather remain exposed to the surroundingarticular cartilage in the space between the bone and the insert. Thetop surface 40 of the insert 16 is exposed to the joint spaceenvironment. The top portion of the exterior surface of the deliveryunit 14 laterally abuts either the top portion of the exterior surfaceof an adjacent delivery unit 14 or undamaged articular cartilage (whenplaced adjacent a peripheral portion of an area of removed cartilage).The bottom portion of the exterior surface of the elongate member 26 ofthe delivery unit 14 rests on and laterally abuts the subchondral boneplate.

When the cartilage repair system of the invention is placed in an areaof removed damaged articular cartilage, through the subchondral boneplate into the cancellous bone, communication is established between thehealthy cancellous bone and the damaged articular cartilage area via achondrogenic growth-supporting matrix—namely, the insert 16. Thispermits vascular invasion and cellular migration, which results inregeneration of the articular cartilage. The regenerated articularcartilage is functionally similar to undamaged articular cartilage. Thecartilage repair system of the invention is bio-absorbed over time andtherefore need not be surgically removed during or after cartilageregeneration. The absorption rate is formula controlled and can rangefrom 6-12 weeks to one year or more depending on its site-specificapplication.

As the basic bio-absorbable composition of the insert 16 degrades orhydrolyzes over time, any repair factors contained therein areprogressively released into the site, thus further promoting cellularregeneration. Cellular regeneration occurs throughout the insert.

Referring now to FIG. 6 in particular, therein illustrated is a secondembodiment 10A of the system of the present invention. In thisembodiment 10A the functions of the insert 16 and porous film 22 areperformed by a single flexible element 16A. The element 16A isillustrated in FIG. 6 in an intermediate stage—that is, as being partlywrapped around the delivery unit 14A. The securing device 20A isinsertable onto the elongate member 26 of the delivery unit 14A so thatthe element 16A is held in place by upwardly projecting locking barbs21A.

The delivery unit 14A differs from the delivery unit 14 in that theelongate member 26A of the delivery unit 14A is circular in crosssection, defines a longitudinally extending plurality of longitudinallyspaced windows 100 therein leading to bore 30A, and has alongitudinally-extending series of circumferentially spaced,radially-extending steps 32A (and no counterpart of flange 70). Thewindows 100 promote communication between the cancellous bone and theinsert 16A, as do the vertical spaces between the steps 32A.

If desired, the retainer 20A may have a slightly different configurationthan retainer 20, with the retainer 20A lacking barbs or projectionsupstanding from the base thereof.

While the first embodiment 10 is shown and described herein as havingthe porous film 22 and insert 16 separate and distinct, the secondembodiment 10A is shown and described herein as having the singleflexible element or wrap 16A combining the insert and the porous filmfunctions. Clearly the choice between a pair of elements 16, 22 or asingle flexible element or wrap 16A for any given delivery unit 14 andretainer 20 is a matter of choice to be made depending upon theparticular application intended.

Referring now to FIGS. 7 and 8 in particular, therein illustrated is athird embodiment 10B of the present invention. The third embodiment 10Bincludes a perforated and preferably porous film 22B, a delivery unit14B (including an elongate member 26B and three radial arms 28B) and apair of inserts 16B (perforated therethrough by several relatively smallholes). The inserts 16B form a sandwich with the support arms 28B whenthe top insert 16B is disposed above the radial arms 28B and the bottominsert 16B is disposed under the radial arms 28B. The support arms 28Bare optionally fewer in number than in support 28 and preferably definetriangles open in the center thereof. The elongate member 26B isprovided with a longitudinally extending series of circumferential steps32B. While the porous film 22B, upper insert 16B, and delivery unit 14Bdefine central apertures 30B, the bottom insert 16B defines a somewhatlarger aperture 30B enabling it to be fit over the elongate member 26B.

Needling of the porous film 22B and the inserts 16B after assembly maysuffice to maintain the assembly elements together, thus avoiding theneed for a retainer 20B. Preferably the needling would occur only inareas not occupied by the material of delivery unit 14B.

Referring now to FIGS. 9 and 10 in particular, therein illustrated is afourth embodiment 10C of the present invention, which dispenses entirelywith the need for either a porous film or wrap 22 or a retainer 20. Inthis embodiment, the delivery unit has a plurality of radially-extendingsupport arms 28C. Each radial arms 28C includes a proximal transversemember 110 and a distal transverse member 114. The proximal transversemember 110 has an enlarged end 112 at each end, while the distaltransverse member 114 has an enlarged end 116 at each end. The enlargedends 112, 116 are beveled to facilitate their passage through theinserts 16C in one direction, while blocking passage therethrough in theopposite direction. During assembly of the system 10C, the elongatemember 26C is passed downwardly through the bottom insert 16C so thatthe enlarged ends 112, 116 of the transverse members 110, 114 passtherethrough and act to hold the lower insert 16C in position. Then theupper insert 16C is brought down on the radial arms 28C with theenlarged upper ends of the proximal transverse members 110 extendinginto the upper insert 16C and the upper enlarged ends 116 of the distaltransverse members 114 extending through the upper insert 16C, therebyto retain the upper insert 16C on the radial arms 28C. To further securethe two inserts 16C and the radial arms 28C together, heat may beapplied to at least partially melt the radial arms 28C. Thus, uponcooling, both inserts 16C and the radial arms 28C bond together.Typically either the transverse members 110, 114 are barbed and amechanical lock is achieved or the transverse members 110, 114 are notbarbed and a melt-based lock is achieved.

Still referring now to FIGS. 9 and 10, the fourth embodiment 10C furtherillustrates a removable delivery unit 14C having a spreadable andretractable elongate member 26C. Thus, the elongated member 26C isdivided or partially split into two components 117. The two components117 are preferably biased towards one another to facilitate introductionof the elongate member 26C into the operative site. Thereafter, however,an element 118 (preferably having a forward tip of wedge shaped design),is inserted from above into the bore 30C of the elongate member 26C viathe inserts 16C. The element 118 may be externally threaded (in whichcase the bore 30C of the elongated member 26C is internally threaded) orit may simply be a nail. In either case, after insertion of the unit 10Cinto the surgical site, the driving of the element 118 through the upperinsert 16C and into the bore 30C of the elongated member 26C spreads thetwo components 117 apart, thereby improving the fixation of the unit 10Cwithin the cancellous bone. Should it ever prove desirable, the element118 may be removed (either by being counter-rotated in the case of athreaded engagement or simply pulled up from a non-threaded engagement),thereby allowing the two components 117 to approach one another andfacilitate removal of the entire insert 10C from the operative site.

Referring now to FIGS. 11-12B, therein illustrated is a fifth embodiment10D of the present invention. The radial support arms 28D are triangularin configuration, with a central opening in each, and are sandwiched byan upper insert 16D and a lower insert 16D. However, instead of beingsecured to the support arms 28D of the delivery unit 14D by barbedstakes and/or heat welding (as in the fourth embodiment 10C), the upperand lower inserts 16D are maintained in place on the radial support arms28D because they are sonically welded together and optionally to thearms 28D. To facilitate this, the upper surface of the upper insert 16Dand the lower surface of the lower insert 16D are provided withcircumferentially spaced indentations 121 which will be positionedbetween a pair of sonic welders 122 during the sonic welding process.(The indentations 121 in the lower insert 16D are visible in FIG. 12B.)The main weld is located between the indentations 121. As sonic weldingis a well known procedure, further details thereof are not deemednecessary therein.

As in the previous embodiments where the bottom insert 16 has to passupwardly over the elongated member 26 of the delivery unit 14, the smallaperture 30D of the lower insert 16D is enlarged in dimension to bereceived over the elongate member 26D.

Referring now to FIGS. 13A and 13B in particular, therein illustrated isa sixth embodiment 10E of the present invention. In the embodiment 10E,at the time of implantation, a delivery unit 14E is partially insertedthrough a single insert 16E disposed over a prepared cancellous bonesite 148 such that the arms 28E extend upwardly and outwardly to fix theinsert 16E to the prepared bone site 148. In the preferred embodimentillustrated, arms 28E hold insert 16E′ in place directly over thedelivery unit 14E. Accordingly, the insert portions 16E and 16E′cooperatively define a substantially continuous insert surface when theassembly is inserted.

Referring now to FIGS. 14 and 15 in particular, therein illustrated is aseventh embodiment 10F of the present invention. The insert 16F includesa relatively rigid, screen-like, bio-absorbable middle layer 130 ofceramic-free, bio-absorbable fabric, and the top of the delivery unit14F defines a plurality of upstanding lugs 132 having spiked tips 134 ofsufficient length to penetrate the fabric layer 130 and thereby hold theinsert 16F in place on the delivery unit 14F. For example, there may besix circumferentially spaced barbed lugs 132 projecting upwardly fromthe top of the delivery unit 14F. Preferably the middle layer 130 issurrounded by upper and lower layers of the insert 16F.

Referring now to FIGS. 16 and 17 in particular, therein illustrated isan eighth embodiment 10G of the present invention. The insert 16Gincludes an upper layer and a lower layer. The delivery unit 14Gincludes a pair of radially extending arms 28G terminating in hooks 136.The hooks 136 extend both upwardly into the upper layer and downwardlyinto the lower layer of the insert 16G. To assemble the unit 10G, theradial arms 28G are interposed between the upper and lower layers of theinsert 16G, and the two elements 28G, 16G are then rotated slightlyrelative to each other in order to cause the hooks 136 to bite into andjoin the upper and lower insert layers. Preferably the upper and lowerlayers of insert 16G contain a plurality of cuts or recesses 138 (equalin number to the plurality of radial arms 28G) which enable the upperand lower layers of the insert 16G to be disposed snugly on theradially-extending arms 28G such that the hooks 136 grab both the topand bottom layers after the delivery unit 14G and the insert 16G arerotated relative to one another.

Referring now to FIGS. 18-20 in particular, therein illustrated is aninth embodiment 10H of the present invention. The embodiment 10H uses asingle layer insert 16H and a delivery unit 14H having at the topthereof a plurality of upwardly and outwardly extending arms 28H (fourbeing shown). The insert 16H is centrally cut or slit appropriately at138 to receive the arms 28H therein when the tips thereof are externallymaintained relatively close together as illustrated in FIG. 18. However,when the tips are released, the downwardly and outwardly biased radialarms 28H flatten somewhat and extend further radially outwardly thanbefore, now extending out of the cut or slit 138 and into the actualmaterial of the insert 16H. In this embodiment it is important that theradially-extending arms 28H be relatively strongly resilient so thatthey enter the insert 16H about the cuts or slits 138 as the deliveryunit 14H and the insert 16H are pressed together and the external forceon the arms 28H is released.

Referring now to FIGS. 21-23, therein illustrated is a tenth embodiment10J of the present invention. The embodiment 10J uses a one-piece insert16J provided with cuts or slits through at least the bottom portionthereof. The delivery unit 14J has at the top thereof a plurality ofradially extending arms 28J, each defining a transversely-extending pairof fingers 142 adapted to fit into cuts 140 of insert 16J. Thus, whenthe insert 16J and the delivery unit 14J are interposed and then rotatedrelative to one another, the fingers 142 bite into the insert 16J inorder to maintain the insert 16J on the delivery unit 14J, asillustrated in FIG. 22 (where the phantom line representation of thedelivery unit 14J indicates the initial position of the arms 28J and thesolid line representation indicates the final position of the arms 28J).

The arms 28 and the elongate member 26 may be of integral, unitary,one-piece construction formed in a single operation, or they may beseparately formed and subsequently joined together to define a deliveryunit 14.

In reviewing the several embodiments described and illustrated, it willbe appreciated that retainer rings 20, 20A and 20B are not required forthe fourth embodiment 10C through the tenth embodiment 10J as theseembodiments 10C-10J lack the film (whether porous or perforated) 22,16A, 22B of the first, second and third embodiments 10, 10A, 10B.Functionally the various retainer rings 20, 20A and 20B of the first,second and third embodiments 10, 10A, 10B, respectively, are with minormodifications interchangeable.

It will further be appreciated that inserts 16 of the first embodiment,16A of the second embodiment, 16E of the sixth embodiment, 16F of theseventh embodiment, 16H of the ninth embodiment, and 16J of the tenthembodiment are of unitary design rather than being composed of twoseparate insert layers (although insert 16F requires the presence of afabric layer 130). By way of contrast, inserts 16B of the thirdembodiment, 16C of the fourth embodiment, 16D of the fifth embodiment,and 16G of the eight embodiment, require a two-part insert with a topinsert layer initially separated from a bottom insert layer.

Of course, the porous film may be formed of and as a part of the insert,as illustrated in insert 16A of the second embodiment.

It will also be understood that while the radial arms may extendoutwardly without forming a closed geometrical figure therebetween (asin arms 28 of the first embodiment, 28A of the second embodiment, 28C ofthe fourth embodiment, 28E of the sixth embodiment, 28G of the eighthembodiment, 28H of the ninth embodiment, and 28J of the tenthembodiment), in some embodiments the radial arms preferably define ageometric pattern—e.g., a triangle which is open in the interior thereof(as in arms 28B of the third embodiment, 28D of the fifth embodiment,and 28F of the seventh embodiment). The open spaces in the closedfigures facilitate communication between the insert thereabove and thecancellous bone therebelow. Where a pair of adjacent arms define aclosed geometrical figure, the arms are more strongly resilient andbetter able to withstand pressures thereon without deflecting orbreaking.

While the radial arms may simply be barbed in a horizontal plane (as inarms 28 of the first embodiment, 28A of the second embodiment, 28B ofthe third embodiment, and to some degree 28E of the sixth embodiment),the radial arms may have barbs in one or both directions in a verticalplane (as in radial arms 28C of the fourth embodiment, 28F of theseventh embodiment, 28G of the eighth embodiment, and to some degree 28Eof the sixth embodiment).

The elongate member or bottom portions of the delivery units arepreferably open at the sides thereof or possessed of windows 100 on thesides thereof (for communication with the internal bore), except for theelongate members 26E of the sixth embodiment and 26J of the tenthembodiment. Where the elongate member is devoid of sides, any retainermeans therefor preferably defines a somewhat elongated central aperturecoaxial with the aperture of the internal bore, as in retainer means 20of the first embodiment. But where the elongate member is essentiallycircular in cross section, as in elongate members 26A of the secondembodiment and 26B of the third embodiment, a retainer means 20A, 20B,respectively, which defines a circular opening 56A, 56B, is preferablyemployed. Alternatively, an equivalent structure may be employed whereinthe insert is barbed (to grip into the retainer means) instead of theretainer means being barbed (e.g., having barbs 21A).

Important considerations in the selection of one embodiment relative toanother include the ease with which a surgeon or other operating roompersonnel may secure together the unit and the insert (including thenumber of different components which must be juggled at once in order toassemble the repair system), the relative costs, the ability of theelongate members of the delivery units to provide exposure of the insertto adjacent inserts, healthy cartilage and cancellous bone, ease ofmanufacture of the components, etc.

The preceding embodiments 10-10J are directed to an assembly of at leasta delivery unit and a matrix or insert, wherein the delivery unitadjacent to the top thereof provides a support for the matrix or insertand adjacent to the bottom thereof provides means for mounting thedelivery unit in cancellous bone. In yet another embodiment of thepresent invention, the delivery unit may be itself a sub-assembly of twoseparately formed components—namely, means for supporting the matrix orinsert and means for anchoring the delivery unit in cancellous bone.

Referring now to FIGS. 24-28 in particular, therein illustrated is aneleventh embodiment 10K of the present invention. Here the radialsupport arms 28K and related support means 26K′ for supporting theinsert 16K are formed separately from the retaining means 26K forfixation to cancellous bone and its related means (outwardly extendingsteps 32K and barbs 21K), as illustrated in the exploded isometric viewof FIG. 26. It will be appreciated that the insert 16K is partially cutaway in FIG. 24 and not shown at all in FIGS. 26-28. The support arms28K and support means 26K′ are secured to the retaining means 26K,extending steps 32K, barbs 21K by a snap-in fastening system or otherconventional means. In the snap-in configuration the support systemdefines adjacent the bottom thereof resilient outwardly extendingprojections 29K adapted to lock the support system in place on thefixation system by an interference fit with outwardly extendingshoulders 33K, which extend above projections 29K when the two systemsare assembled to form a delivery unit, as illustrated in FIGS. 27 and28.

A major advantage of this construction (the eleventh embodiment 10K) isthat a preferred specific design of the radial arms of any of theembodiments (or other means for supporting the insert) may be employedwith a preferred specific design of the means for retaining the deliveryunit in cancellous bone of any of the embodiments (or other means foranchoring the insert support means in cancellous bone), so that anoptimum combination of these two designs for a particular injury in aparticular patient may be selected by the surgeon in the operating roomafter the injury is visualized. For example, the arms of 28K may be ofdiffering lengths or geometries to best fit the defects to beregenerated.

The bio-absorbable cartilage repair system embodiments 10-10K describedabove have been described in the context of a single assembly consistingof a delivery unit and an insert or matrix. However, as will beappreciated by those skilled in the surgical arts, frequently the areaof damaged or destroyed articular cartilage is so great as to requirethe use of more than a single assembly. In this instance, considerableskill on the part of the surgeon is required in order to place the twoassemblies, and in particular the two delivery units, as close to oneanother as possible so as to promote cartilage regeneration over theentire area of damaged or destroyed articular cartilage that has beenremoved. Alternatively, the requisite skill of the surgeon may berendered unnecessary through the use of surgical devices (e.g., spacers)which ensure appropriate placement of the delivery units in the desiredside-by-side relationship. Such surgical devices are not part of theassemblies themselves, must be removed after the assemblies have beenproperly positioned in the patient, and, at least to some degree,interfere with visualization of the work area by the surgeon.Accordingly, the present invention also encompasses bio-absorbablecartilage repair systems which in effect utilize a plurality of deliveryunits and ensure that the delivery units will be appropriatelypositioned in the work area, like tiles, with a minimum of effort by thesurgeon.

In order to effect this result, two distinct novel approaches areutilized.

Referring now to FIGS. 29-32, therein illustrated is a twelfthembodiment 10L of the present invention in the form of a duplexassembly. For the purposes of illustrating the principle of this duplexembodiment, it is only necessary to recognize that there are at leasttwo delivery units 14L, 14L′ and a single insert 16L. The insert 16Lextends over both of the delivery units 14L and 14L′, as best seen inFIG. 30, and is preferably “8” shaped so as to provide full coverage ofeach delivery unit 14L, 14L′ and a minimum width conjoining or juncturearea 150L therebetween. For example, two delivery units 14L, 14L′ havingdiameters of about 7-9 mm may be connected by an insert or matrix 16Ldefining a juncture or conjoining area 150L having a width of about 4mm.

The duplex assembly 10L can be folded at the conjoining area 150Lthrough an angle of approximately 180° so that the two delivery units14L, 14L′ are approximately on a common longitudinal axis, althoughpointed in opposite directions. As illustrated in FIGS. 31-32, theduplex assembly 10L, may be positioned in the patient in its foldedstate (for example, through a tubular applicator) and then, asillustrated in FIGS. 29-30, unfolded in the work area so that thedelivery units 14L, 14L′ thereof are closely adjacent and preferably ina side-by-side contiguous relationship. Once one of the delivery units14L, 14L′ of the duplex assembly 10L has been properly positioned in thework area, appropriate positioning of the other delivery unit 14L′, 14Lis automatic with unfolding of the duplex assembly 10L.

As illustrated in FIG. 33, two or more duplex assemblies 10L may bedisposed in staggered contiguous relationship, if desired. Asillustrated in FIGS. 33 and 34, a duplex assembly 10L may be in acontiguous relationship with a non-duplex assembly 10.

It will be appreciated that while the description above relates only tothe placement of two delivery units 14L, 14L′ in a contiguousside-by-side relationship, additional assemblies (whether of the same ordifferent types) may be placed in contiguous relationship thereto inorder to effect a complete tiling of the damaged articular cartilagearea to be regenerated.

Referring now to FIGS. 35-36, therein illustrated is a thirteenth orcompressible embodiment 10M of the present invention having a deliveryunit 14M wherein the flexible, radially extending support arms 28M areof a spiral or helical design and resiliently compressible. In twodimensional terms, each support arm 28M describes a curve on a planethat winds around a fixed center point at a continuously increasingdistance from the point; in three-dimensional terms, each support arm28M describes a three-dimensional curve that lies on a cone extendingthrough a longitudinal axis (e.g., the delivery unit axis) so that itsangle to a plane perpendicular to the longitudinal axis is constant. Forthe purpose of illustrating the principle of this compressibleembodiment 10M with spiral or helical support arms 28M, it is onlynecessary to recognize that at least one support arm 28M is biasedoutwardly at its free end (typically due to the resiliency of thesupport arm material) but resiliently displaceable inwardly under manualpressure.

Preferably, as illustrated, there are four support arms 28M so that eachsupport arm extends over only a fourth of the circumference of thedelivery unit 14M, although a greater or lesser number of support arms28M may be used. As illustrated, the four support arms 28M have anoctagonal matrix or insert 16M wrapped thereabout to provide an overallhexagonal appearance to the top of the assembly 10M, although a matrixor insert 16M having a greater or lesser number of sides may be used.

While the assemblies of FIGS. 1-36 have been described hereinabove aspreferably being polygonal or at least partially polygonal at the levelof the insert so as to enable adjacent and even contiguous placement ofa plurality of assemblies, clearly almost any of such assemblies mayinstead be substantially circular. For example, in a variant of thethirteenth embodiment 10M illustrated in FIGS. 37-42 the peripheralconfiguration is circular. A circular configuration for the upperportion of the assembly facilitates the procedure for creating thecavity into which the assembly will be placed. A circular drill or thelike may be used to create the circular cavity rather than the chiselrequired to form the polygonal cavity.

After one such circular assembly 10M in compacted configuration (FIG.37) has been properly positioned in the work area, a second suchcircular assembly 10M′ in compacted configuration may be placed in thework area with the second assembly 10M′ being closely adjacent orcontiguous to the first assembly 10M, such that portions of the outerperipheries of the later expanded first and second assemblies 10M, 10M′attempt to occupy the same space, with the inevitable result that thereis necessarily an inward flexing of at least one adjacent radial arm 28Mof one expanded assembly 10M, at least one adjacent radial arm 28M′ ofthe other expanded assembly 10M′, or the adjacent radial arms 28M, 28M′of both expanded assemblies 10M, 10M′ (FIG. 40). The helical or spiraldesign of the radial arms of the thirteenth embodiment 10M enables aneasy adjustment of the effective diameter of the assembly, thereby toenable a plurality of such assemblies to be closely positioned withinthe work or tiling area.

If desired, as illustrated, additional assemblies 10M of this type maybe added as necessary to fill the work or tiling area. Naturally, thistype of assembly 10M may also be used in conjunction with the previouslydescribed assemblies, with the understanding that substantially all ofthe resilient compression of the support arms will occur in the assemblyof this type.

When it is necessary to insert two such circular assemblies 10M, 10M′side by side, a problem arises because the peripheries of the twocircular assemblies will contact only tangentially, thereby leaving asubstantial area which will not directly receive the benefit of theassemblies. In order to overcome this tiling problem (which typicallyarises only when two or more circular assemblies 10M are to be placed inadjacent or contiguous positions), the support arms 28M of at least onesuch circular assembly and preferably the support arms 28M of both suchcircular assemblies, are flexible. Thus the peripheries of the circularassemblies 10M may be placed close together, and even in a somewhatoverlapping relationship, because the overlapping peripheral portion ofat least one circular assembly (and preferably both circular assemblies)is capable of deflecting (i.e., flexing vertically) to accommodate theoverlapping peripheral portion of the other circular assembly. Moreparticularly, at least one support arm 28M of the circular assembly isflexible or at least deflectable. The extent of the delectability orflexibility of the circular assembly may be controlled by the tightnessof the porous film or wrap 22M about the support arms 28M, a looser wrapresulting in more deflectable support arms.

Installation of the thirteenth embodiment 10M, 10M′ is facilitated bymaintaining each assembly in a tightly compressed or compact state (asby keeping it within a removable hollow cylindrical tube 160) andinstalling as many adjacent assemblies in the compressed or compactstate as necessary in the work area before removal of the hollow tube160 from each assembly, with the resultant expansion of the support arms28M, 28M′.

Alternatively, as illustrated in FIGS. 41-43, after assembly 10M in thecompacted state (FIG. 41) is installed in the work area, the compressingmeans 160 is removed therefrom. Then an adjacent assembly 10M′ in thecompacted state (FIG. 42) is installed, with the surgeon (or the shapeof the forward tip of compressing means 160) shoe horning or displacingany portion of a support arm 28M of the first assembly 10M fromunderneath the compressing means 160 of the adjacent assembly, afterwhich compressing means 160 is then removed therefrom (FIG. 43). Whilethe former insertion procedure (see FIGS. 39-40) is less demanding onthe skills of the surgeon than the latter insertion procedure ( seeFIGS. 41-43), it also requires a greater surgical exposure of the workarea along with the obvious disadvantages thereof

As will be appreciated by those skilled in the art, the compressibilityof the delivery unit 14M minimizes the demand upon the skill of thesurgeon for proper placement of the assemblies, as a group of compressedassemblies 10M which are somewhat misplaced can still adequately cover awork area without any interruption when allowed to expand. It will alsobe readily appreciated by those skilled in the art that the assembly 10Mdescribed above will have utility not only in the environment where twoassemblies will be closely positioned, but even in the environment of asingle assembly. For example, it may be desirable to maintain anassembly 10M in a compressed form during insertion into the patient,with the assembly then being allowed to expand.

While the preceding embodiments are directed to an assembly of at leasta delivery unit and a matrix, the product may also be made as a single,unitary and integral product. To accomplish this, the intended productis first visually modeled in three dimensions on a computer as acomputer aided design (CAD) file or, alternatively, data available fromlaser, x-ray, CAT or MRI scans can be imported into the CAD system andused in the design process. The resulting design is then used as thebasis for engineering analysis and evaluation, using computer aidedengineering (CAE) tools designed to work with CAD geometries. The finalCAD data is then transferred to a machine which translates the CAD datainto layer-by-layer information and then executes the motions to producethe final product. The fabrication of the intended product isaccomplished with repeated cycles of spreading powder, selectivelydepositing binder on portions of the powder, and removal of unboundpowder. The product is thus built vertically, layer-by-layer, preferablyusing photolithography techniques. The result is a product design thatcan be efficiently evolved to a final product form with the desiredfeatures and performance characteristics.

Accordingly, the term “assembly” is used in the specification and claimshereof to encompass both elements which are independently formed andthen combined together, or elements which have been created in a singleprocess, layer-by-layer, as disclosed above.

The term “bio-absorbable” is used in the specification and claims hereofto indicate a material which will be degraded or absorbed by the bodysuch that regenerated articular cartilage thereabout is functionallysimilar to non-damaged articular cartilage.

The term “dimensionally stable” as applied to a material is used hereinto indicate that the material does not appreciably expand in synovialjoint fluid due to the absorption thereof. While there may be someslight dimensional expansion even under this definition, it is aninsufficient amount of expansion to enable retention of the material byits environment (for example, the delivery unit in the case of theinsert, and the adjacent healthy area of articular cartilage andsubchondral cancellous bone in the case of the delivery unit).

While the assembly of the present invention has been describedhereinabove as preferably having the insert 16 and the delivery unit 14joined together prior to surgical implantation in a patient, the presentinvention also contemplates the initial surgical implantation of thedelivery unit 14 (without the insert) followed by a subsequent additionof the insert 16 to the delivery unit 14 in situ. Embodiments of thepresent invention especially well suited for such in situ joining of aninsert and a delivery unit are illustrated in FIGS. 14-15, 18-20 and21-23.

Either through a lack of surgical skill or, in certain instances,intentionally (e.g., where the depth of the cancellous bone isinsufficient to provide suitable anchoring for the delivery unit wheninserted at a suitable angle to properly position the insert), off-axisplacement of the shaft or stem of delivery unit may result in anon-flush curvature of the top of the insert with the adjacent healthycartilage. Referring now to FIG. 45, the present invention thereforeadditionally encompasses a fourteenth embodiment 10P which has adelivery unit 14P with a shaft or stem 80P and a swivel or pivotablehead 82P. The distal end of the delivery unit shaft 80P defines a ballor ball-like surface 84P, and the proximal end of the delivery unit head82P defines a socket or socket-like surface 86P adapted to receive andretain the ball 84P. The insert 16P is wrapped around the delivery unithead 82P and secured thereto by a retainer ring 20P or like structureperforming the same function. Thus, if the delivery unit shaft 80P hasbeen inserted into the cancellous bone at an angle such that the insert16P within the head portion 82P is not aligned with the cartilagesurface—either through accident or intentionally—the delivery unit head82P may be swivelled or pivoted relative to the delivery unit shaft 80P,thereby enabling the insert 16P to be aligned with the healthy articularcartilage surface while the shaft 80P is fixedly retained in thecancellous bone. Preferably the distal end of the delivery unit shaft80P and the proximal end of the delivery unit head 82P are beveled topermit head inclinations of at least 15 degrees in either direction, andthe removed cartilage and bone area is large enough to accommodate suchswivelling. It will be appreciated that this swivel head orball-and-socket embodiment 10P enables the assembly of the presentinvention to be utilized even where the cancellous bone is inadequate indepth to receive a delivery unit shaft extending normal thereto, as thedelivery unit shaft may be implanted in the cancellous bone at anon-normal or inclined angle so as to make maximum use of the availablebone, and the delivery unit head then swivelled (relative to thedelivery unit shaft) to provide an optimum orientation relative to theremaining cartilage.

Each of the several embodiments shown and described herein includesparticular structural features and offers particular functionaladvantages. As will be apparent to those skilled in the art, theparticular structural features and the particular functional advantagesof one given embodiment may generally be used in conjunction withanother embodiment to provide that other embodiment with the same orlike structural features and functional advantages. By way of example,in general the retainer means of one embodiment may be substituted forthe retainer means of another embodiment, and the delivery unit of oneembodiment may be substituted for the delivery unit of anotherembodiment.

Further, one embodiment of the present invention encompasses a cartilageand bone repair system to be mounted both in an area of damaged ordestroyed articular cartilage and damaged subchondral bone, and anadjacent healthy area of articular cartilage and cancellous; bone. Thesystem comprises an assembly of a bio-absorbable delivery unit and aporous bio-absorbable insert. The delivery unit is formed ofbio-absorbable material. The delivery unit has a central body and aplurality of radially extending support arms projecting outwardly fromthe central body and configured to support the insert. The insert issupported by the delivery unit, is formed of bio-absorbable materialsand establishes communication between the removed area of bone andcartilage and the adjacent healthy area for a chondrogenic andosteogenic growth supporting matrix. The matrix may be one layer or abilayer where the lower layer is designed to create an osteogenicsupporting matrix and the upper layer is designed to create achondrogenic supporting matrix. indeed even a single layer matrix mayfunction as a bilayer—e.g., when the upper portion is pre-dipped in aliquid chondrogenic support and the lower portion is pre-dipped in aliquid osteogenic support.

In a further embodiment each layer could be impregnated as appropriatewith chondrogenic repair factors or osteogeneric repair factorsincluding demineralized bone, BMP's, TCP, TAFB, etc.

To summarize, the present invention provides a system for regeneratingarticular cartilage wherein the regenerated articular cartilage isfunctionally similar to non-damaged articular cartilage and thereforereplaces damaged or destroyed articular cartilage without employingcement or a non bio-absorbable prosthetic device.

Now that the preferred embodiments of the present invention have beenshown and described in detail, various modifications and improvementsthereon will become readily apparent to those skilled in the art.Accordingly, the spirit and scope of the present invention is to beconstrued broadly and limited only by the appended claims, and not bythe foregoing specification.

We claim:
 1. A bio-absorbable cartilage repair system for regeneratingdamaged or destroyed articular cartilage on a joint surface of a bone byestablishing a chondrogenic growth-supporting matrix between an area ofdamaged or destroyed articular cartilage that has been removed and anadjacent healthy area of articular cartilage and subchondral cancellousbone, said system comprising a delivery unit and a porous insert; (A)said delivery unit being formed of bio-absorbable material andconfigured and dimensioned to be mounted in both an area of damaged ordestroyed articular cartilage that has been removed and an adjacenthealthy area of articular cartilage and cancellous bone, said deliveryunit having a central body and a plurality of radially extending,flexible support arms projecting outwardly from said central body andconfigured and dimensioned to support said insert; and (B) said insertbeing formed of bio-absorbable material and establishing communicationbetween the removed area and the adjacent healthy area for achondrogenic growth-supporting matrix.
 2. The system of claim 1 whereinsaid support arms have upper, lower, and outer surfaces and wherein saidinsert is disposed on the upper, lower and outer surfaces of saidsupport arms.
 3. The system of claim 1 wherein said support arms havefree ends circumferentially spaced from one another to define areas forreceipt of a chondrogenic growth-supporting matrix.
 4. The system ofclaim 1 wherein said support arms have circumferentially spaced freeends adapted to engage and at least partially spatially stabilize saidinsert.
 5. The system of claim 1 wherein said support arms have freeends and wherein the free ends are horizontally barbed.
 6. The system ofclaim 1 wherein said support arm free ends are vertically barbed.
 7. Thesystem of claim 1 wherein said insert has a top, a bottom and a sidewallconnecting said top and bottom, said bottom allowing vascular invasiontherethrough, and said top and sidewall allowing cellular migration. 8.The system of claim 7 wherein said sidewall is polygonal in plan.
 9. Thesystem of claim 7 wherein said sidewall is circular in plan.
 10. Thesystem of claim 1 wherein each of said delivery unit and said insertessentially consist of completely bio-absorbable material which isdimensionally stable in synovial joint fluid against expansion due tothe absorption thereof.
 11. The system of claim 1 additionally includingretainer means securing said insert to said delivery unit.
 12. Thesystem of claim 11 wherein said retainer means is secured to a portionof said central body below said insert and bears upwardly against saidinsert.
 13. The system of claim 11 wherein said retainer meansessentially consists of completely bio-absorbable material which isdimensionally stable in synovial joint fluid against expansion due tothe absorption thereof.
 14. The system of claim 1 comprising a porousfilm formed of bio-absorbable material securing said insert to saiddelivery unit.
 15. The system of claim 14 wherein said porous film has acentral film portion disposed over said insert and a plurality of filmfingers projecting outwardly from said central film portion, downwardlyand inwardly, under said support arms.
 16. The system of claim 15comprising retainer means secured to a lower part of said central bodyand bearing upwardly against said film fingers.
 17. The system of claim14 wherein said porous film essentially consists of completelybio-absorbable material which is dimensionally stable in synovial jointfluid against expansion due to the absorption thereof.
 18. The system ofclaim 1 wherein said central body comprises a plurality of outwardlyextending flanges.
 19. The system of claim 1 wherein said insert is aflexible porous film formed of bio-absorbable material secured to saiddelivery unit.
 20. The system of claim 19 wherein said porous film has acentral film portion disposed over said support arms and a plurality offilm fingers projecting outwardly from said central film portion,downwardly and inwardly, under said support arms.
 21. The system ofclaim 20 additionally including retainer means secured to a lower partof said central body and bearing upwardly against said film fingers. 22.The system of claim 19 wherein said porous film essentially consists ofcompletely bio-absorbable material which is dimensionally stable insynovial joint fluid against expansion due to the absorption thereof.23. The system of claim 1 wherein said central body defines an apertureextending longitudinally therethrough.
 24. The system of claim 23wherein said insert defines an aperture extending longitudinallytherethrough.
 25. The system of claim 23 additionally including retainermeans secured to a lower part of said central body and bearing upwardlyagainst said insert, said retainer body defining an aperture extendinglongitudinally therethrough coaxial with said central body aperture. 26.The system of claim 23 additionally including a porous film consistingsubstantially of completely bio-absorbable material securing said insertto said delivery unit, said porous film defining an aperture extending,longitudinally therethrough coaxial with said central body aperture. 27.The system of claim 23 wherein said insert is a flexible porous filmconsisting substantially of completely bio-absorbable material securedto said delivery unit, said porous film defining an aperture extendinglongitudinally therethrough coaxial with said central body aperture. 28.The system of claim 1 wherein at least a portion of said delivery unitcentral body disposed below said insert defines flexible legs, saidsystem additionally including means for moving said legs from ahorizontally retracted orientation enabling removal of said assembly toa horizontally expanded orientation fixing said assembly in place. 29.The system of claim 28 wherein said flexible legs are resilient, andsaid moving means is retractable to enable movement of said legs fromsaid expanded orientation to said retracted orientation.
 30. The systemof claim 1 wherein said insert includes cartilage orcartilage-progenitor cells to facilitate establishing saidcommunication.
 31. The system of claim 1 wherein said delivery unit isprovided by two separately formed components, one of said componentsbeing configured and dimensioned to be mounted in both an area ofdamaged or destroyed articular cartilage that has been removed and anadjacent healthy area of articular cartilage and cancellous bone, andthe other component providing the central body and plurality of radiallyextending, flexible support arms projecting outwardly from said centralbody and configured and dimensioned to support said insert.
 32. Thesystem of claim 31 wherein said delivery unit includes retainer meansfor bearing on a portion of said insert intermediate said two componentsto lock said insert portion in place.
 33. The system of claim 31 whereinsaid delivery unit is assembled with said insert prior to use.
 34. Thesystem of claim 31 wherein said one component defines a longitudinalaperture therethrough, and said central body of said other component isconfigured and dimensioned to at least partially pass through saidaperture.
 35. The system of claim 31 wherein at least one of saidcomponents includes means for retaining said components together afterassembly.
 36. A bio-absorbable cartilage repair system for regeneratingdamaged or destroyed articular cartilage on a joint surface of a bone byestablishing a chondrogenic growth-supporting matrix between an area ofdamaged or destroyed articular cartilage that has been removed and anadjacent healthy area of articular cartilage and subchondral cancellousbone, said system consisting essentially of two delivery units and asingle flexible porous insert; (A) each of said delivery units beingformed of bio-absorbable material and configured and dimensioned to bemounted in both an area of damaged or destroyed articular cartilage thathas been removed and an adjacent healthy area of articular cartilage andcancellous bone, each said delivery unit having a central body and aplurality of radially extending, flexible support arms projectingoutwardly from said central body and configured and dimensioned tosupport said insert; and (B) said insert being formed of flexiblebio-absorbable material and establishing communication between theremoved area and the adjacent healthy area for a chondrogenicgrowth-supporting matrix; said delivery units being configured anddimensioned to enable them to be disposed facing each other andconnected only by said insert for insertion into a patient and thenunfolded to enable them to be separately mounted side-by-side.
 37. Thesystem of claim 36 wherein said insert defines a pair of insertportions, each said insert portion extending over the top of arespective one of said delivery units, and a connecting portion ofreduced width foldably connecting said insert portions together.
 38. Abio-absorbable cartilage repair system for regenerating damaged ordestroyed articular cartilage on a joint surface of a bone byestablishing a chondrogenic growth-supporting matrix between an area ofdamaged or destroyed articular cartilage that has been removed and anadjacent healthy area of articular cartilage and subchondral cancellousbone, said system comprising a delivery unit and a porous insert; (A)said delivery unit being formed of bio-absorbable material andconfigured and dimensioned to be mounted in both an area of damaged ordestroyed articular cartilage that has been removed and an adjacenthealthy area of articular cartilage and cancellous bone, said deliveryunit having a central body and a plurality of inwardly compressibleflexible support arms projecting outwardly from said central body andconfigured and dimensioned to support said insert; and (B) said insertbeing formed of bio-absorbable material and establishing communicationbetween the removed area and the adjacent healthy area for achondrogenic growth-supporting matrix.
 39. The system of claim 38comprising at least two of said delivery units, each said delivery unitbeing mounted side-by-side such that at least one support arm of one ofsaid delivery units inwardly compresses at least one support arm of theother of said delivery units.
 40. The system of claim 39 wherein said atleast one support arm of said one delivery unit would overlap said atleast one support arm of said other delivery unit if at least one of thesupport arms was not inwardly compressed.
 41. The system of claim 39wherein said insert and said support arms are deflectable.
 42. Thesystem of claim 1 wherein a top layer of said insert contains achondrogenic growth-supporting matrix and a lower portion of said insertcontains an osteogenic growth-supporting matrix, the insert configuredand dimensioned to be disposed with said chondrogenic growth-supportingmatrix adjacent a healthy area of articular cartilage and saidosteogenic growth-supporting matrix adjacent a healthy area ofsubchondral cancellous bone, thereby establishing chondrogenic andosteogenic growth-supporting matrices in removed areas of damaged ordestroyed articular cartilage and subchondral bone, respectively.
 43. Abio-absorbable cartilage repair system for regenerating damaged ordestroyed articular cartilage on a joint surface of a bone byestablishing a chondrogenic growth-supporting matrix between an area ofdamaged or destroyed articular cartilage that has been removed and anadjacent healthy area of articular cartilage and subchondral cancellousbone, said system comprising an assembly of a delivery unit and a porousinsert; (A) said delivery unit being formed of bio-absorbable materialand configured and dimensioned to be mounted in both an area of damagedor destroyed articular cartilage that has been removed and an adjacenthealthy area of articular cartilage and cancellous bone, said deliveryunit having a central body and a plurality of radially extending,flexible support arms projecting outwardly from said central body andconfigured and dimensioned to support said insert; (B) said insert beingformed of bio-absorbable material and establishing communication betweenthe removed area and the adjacent healthy area for a chondrogenicgrowth-supporting matrix; and said delivery unit including a headportion and a stem portion, said head and stem portions being pivotallyjoined together.
 44. The system of claim 43 wherein one of said portionsdefines a ball and the other of said portions defines a socket.
 45. Thesystem of claim 44 wherein said stem portion defines a ball at a distalend, and said head portion defines a socket at a proximal end, said ballbeing pivotally maintained in said socket such that said head portion ispivotable relative to said stem portion.